Direct Conversion Of Chemical Energy Research Articles

Effects of Manganese Oxides on the Activity and Stability of Ni-Ce0.8Sm0.2O1.9 Anode for Solid Oxide Fuel Cells with Methanol As the Fuel

Solid oxide fuel cells (SOFCs) are one of the most promising devices for the direct conversion of chemical energy in fuels into electric power[1]. The Ni-based cermet has been considered as the most promising anode material for SOFCs due to its high catalytic activity, sufficient electrical conductivity and low cost[2]. However, Ni-based anodes face a severe problem of carbon deposition when fueled with hydrocarbons[2]. In this work, Ni-MnOx-Ce0.8Sm0.2O1.9 (SDC) is synthesized with a hydrothermal method and investigated as the anode material of an SOFC fed with methanol. The lowest anodic polarization resistance is obtained when the molar ratio of Mn to Ni is 0.05:0.95. The single cell with that anode and SDC-carbonate composite electrolyte exhibits a maximum power density of 722 mW cm-2 at 700 oC (Fig. 1). The high catalytic activity is attributed to the transfer of electrons from Ni to Mn and the increase of the content of the lattice oxygen in the anode. Mn also increases the resistance to carbon deposition of the anode due to the high lattice oxygen content and the redox cycle of the Mn species. The stability of the single cell is enhanced with the increase of the content of Mn in the anode. Fig.1 I–V and I-P curves of the fuel cells with various anodes at 700 °C with methanol as fuel. References A. Sin, E. Kopnin, Y. Dubitsky, et al., Journal of Power Sources, 2007, 164: 300–305.Z. Wang, W. Weng, K. Cheng, et al., Journal of Power Sources, 2008, 179: 541-546.S. Alayoglu, K. An, G. Melaet, et al., The Journal of Physical Chemistry C, 2013,117: 26608-26616. Figure 1

Fuel Cell Modeling Strategic Roadmap: A Systematic Approach

Polymer electrolyte fuel cells (PEFCs) are promising electrochemical devices for the direct conversion of chemical energy of a fuel into useful electrical work with vast applications in automotive, stationary, and autonomous power. It is widely recognized that progress in PEFC technology is a multi-disciplinary challenge and hinges on Research and Development (RD Services; Products; High Level Targets; Technology; Science; and Enablers and Resources. This study contributes to a much needed foundation for further planning of potential R&D and demonstration projects of fuel cells for automotive and other emerging sectors.

Surface Analytical Investigation of Inner and Outer Surfaces of Porous Components for Polymer Electrolyte Membrane Fuel Cells

Fuel cells allow the direct conversion of chemical energy (typically hydrogen and oxygen or air) to electrical energy and therefore are an important high efficiency option for future energy systems. The surface composition is related to the surface properties, which influence the catalytic and hydrophobic behavior. In polymer electrolyte membrane fuel cells, several components are porous, namely the gas diffusion layer consisting of carbon structure as support and a micro porous layer (MPL) and the catalyst layer (CL). The porous structure is important for the transport of the reactants (hydrogen and air) and products (water) as well as for the electrochemical reactivity at the interfaces. Caused by the porous structure not only the properties of the outer surfaces but also the properties of the inner surfaces are important. The combination of two different depth profiling techniques, ion etching and peel-off by an adhesive tape, and a surface sensitive analytic method, here X-ray photoelectron spectroscopy (XPS), allows to investigate the inner and outer surfaces. XPS allows to determine the chemical composition of the surfaces, which allows to derive information about the hydrophobic/hydrophilic properties. With the ion etching the structure of the surface layer will be investigated with a depth resolution in the range of nanometers in order to determine gradients in the surface compositions, e.g. thin films covering surface of the catalyst particles. The tape peel-off preparation allows to remove a film from the surface and gives the access to the inner surfaces. The surface compositions of the different surfaces prepared with and without tape peel-off of various porous fuel cell components were determined by XPS depth profiles with ion etching. The MPL and the CL consist of a fluorine rich polymer (PTFE or Nafion with a PTFE backbone) and carbon black. In the case of the catalyst layer the carbon black is used as support for the platinum catalyst and in case of MPL as porous conductive material. The fluorine rich compound is used to tailor the hydrophobicity of the components. XPS profiles measured by ion etching of the outer surface and an inner surface of a catalyst layer prepared by an inkjet printing process [1] will be presented. In the C 1s spectra two different carbon species can be distinguished, the signal from carbon black and the carbon signal from the carbon in a fluorine rich compound. The outer and inner surface show a very similar composition and depth profile. The concentrations of the fluorine rich carbon compound and of fluorine itself strongly decrease during the ion etching while the concentrations of the carbon black as well as of the platinum increase. This means that the outer surface as well as the inner surface have a higher concentration of polymer on the surfaces than in the bulk material, whereas the thin polymer film partially covers the Pt catalyst. This behavior is frequently observed for catalyst layers prepared from an ink mixed of the polymer, carbon supported catalyst and solvents [2]. Acknowledgement The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for Fuel Cell and Hydrogen Joint Technology Initiative under Grant No. 303452 (IMPACT).

Challenges in the development of reversible solid oxide cell technologies: a mini review

AbstractHigh‐temperature solid oxide cells (SOCs) are attractive for storage and conversion of renewable energy sources by operating reversibly in solid oxide fuel cell and solid oxide electrolysis cell modes. Solid oxide fuel cell is the most efficient energy conversion device for the electricity generation by electrochemically direct conversion of chemical energy of fuels such as hydrogen, methanol and methane, while under solid oxide electrolysis cell operation mode, hydrogen or syngas can be produced as fuels or feedstock for liquid fuels such as methanol, gasoline and diesel using electricity from renewable energy sources. This mini review will introduce briefly the principle, status and progress in the electrochemical energy conversion and storage process by reversible operation of high temperature SOCs. The challenges in key material and performance degradation issues associated with high‐temperature fuel cell and electrolysis operation of SOCs will be concisely reviewed and discussed. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

A Study of Pt and Pt-Alloy Fuel Cell Catalyst Degradation in Aqueous and Membrane Electrode Assembly Environments Using In Situ Anomalous Small-Angle X-Ray Scattering

Polymer electrolyte membrane (PEM) fuel cells are an attractive energy conversion technology due to their high energy efficiency resulting from direct conversion of chemical energy into electrical energy. However, their cost effective implementation, especially for automotive power, has been hindered by degradation of the electrochemically-active surface area (ECA) of the Pt nanoparticle electrocatalysts. While numerous studies using ex-situ post-mortem techniques have provided insight into the effect of operating conditions on ECA loss, the governing mechanisms and underlying processes are not fully understood. Toward the goal of elucidating the electrocatalyst degradation mechanisms, we have successfully followed Pt nanoparticle growth during potential cycling of the electrocatalyst in an aqueous acidic environment and in a membrane electrode assembly (MEA) environment using in-situ anomalous small-angle X-ray scattering (ASAXS).1 Several catalysts were utilized in this study with varying mean particles sizes; a commercial carbon-supported platinum (20 wt% Pt on XC-72 Vulcan carbon, E-Tek) with a mean particles size of ~2 nm, along with 40 wt% Pt and Pt3Co nano-particles supported on Akzo Nobel Ketjen EC300J carbon black (provided by Johnson Matthey) with a mean particle size of ~3 nm and ~6 nm, respectively. Various potential cycling protocols (triangle, square, and trapezoidal) were applied to aqueous and MEA environments with anodic potential limits in the range of 1.0 to 1.1 V.As an example of the results that will be discussed, ASAXS patterns were analyzed and found that the dominant Pt surface area loss mechanism was found to be preferential dissolution or loss of the smallest particles with varying extents of re-precipitation of the dissolved species onto existing particles in both environments. Correlation of ASAXS-determined particle growth and dissolved Pt measurements in the aqueous environment with both calculated and voltammetrically-determined oxide coverages.2This demonstrates that the oxide coverage is playing a key role in the dissolution process and in the corresponding growth of the mean Pt nanoparticle size and loss of ECA.After extended cycling, the MEA environment showed accelerated degradation as compared to the aqueous stagnant environment (23% to 10% geometric surface area loss after 1,000 potential cycles). Introduction of electrolyte flow to the aqueous cell helped accelerate the Pt growth process to become similar to that observed in the MEA (24% geometric surface area loss after 1,000 potential cycles).These results along with others including those with the Pt3Co catalyst will be discussed in order to shed light on the Pt degradation mechanisms in all environments.Acknowledgements: The authors would like to acknowledge Sarah Ball, Jonathan Sharman, Brian Theobald, and Graham Hards from Johnson Matthey Fuel Cells for supplying the catalysts and catalyst coated membranes. The authors also acknowledge funding from the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Program (Nancy Garland, Technology Development Manager) and the U.S. Department of Energy, Office of Basic Energy Sciences for support of the Advanced Photon Source.ReferencesT. Narayanan, Soft Matter: Scattering, Imaging, and Manipulation. 1st ed.; Springer: Berlin, 2007. J. Gilbert, N. Kariuki, R. Subbaraman, A.J. Kropf, M. Smith, E. Holby, D. Morgan, D. Myers, 2012, J Amer Chem Soc, 134, 36.

Preparation of Platinum Catalyst Supported on Porous Carbon Nanofibers

Low-temperature fuel cells have been attracting more and more attentions for the direct conversion of chemical energy into electricity. Efficiencies of fuel cells to a great extent depend on the activity of the catalytic platinum and its alloys. Increasing the reaction surface area and decreasing the diameter of platinum particles can enhance the activity of the platinum. In this paper, we report a platinum catalyst supported on porous carbon nanofibers. Two kinds of PAN terpolymers with various molecular weights of 15 kDa (PAN-1) and 30 kDa (PAN-2) were first prepared by aqueous precipitation polymerization. The mixtures of PAN with various molecular weights and PMMA were then electrospun, stabilized and carbonized to provide the porous carbon nanofibers. It was found that the PAN with lower molecular weight results in the even fibrous surface and thick diameter, indicating a stable spinning process. Moreover, the PAN-based carbon nanofibers were immersed into a platinum complex solution to support the platinum positive ions. After calcination, the platinum ions deposited on the carbon nanofibers were converted into nanoplatinum particles to provide the platinum catalyst supported on the porous carbon nanofibers.

How Reactive are Metal Surfaces in Solution? A Comparison of the Electrochemical Adsorption of Organic Molecules on Pt At Low Potentials

IntroductionTransition metal surfaces are widely employed as catalysts ofchemical reactions, both at the metal/gas [1] and at the metal/solution [2] interfaces. Well-known examples are ceramic-supportedcatalystsusedingasexhaustsofvehiclestooxidizepartially burnt fuels [3] and metal-based catalysts used in fuelcell devices to promote electrochemical oxidation of organicmolecules for direct conversion of chemical energy into elec-trical energy with high efficiency [4].In this context, the electrochemical oxidation of alcoholshasbeenextensivelystudiedinthelastdecades[5]duetotheirpotentialfor practical applicationsinfuelcells.Directalcoholfuelcell(DAFC),especiallydirectethanolfuelcell(DEFC),isbecominga veryattractivealternative energysourcefor fossilfuel combustion engines due to several advantages, includingits high theoretical efficiency, high energy density of alcohols(comparable to gasoline) [6], and the possibility of energyproduction from renewable sources [7]. However, for theDEFC to become commercially attractive, a few issues mustbeovercome.Oneofthedifficultiesisthatthecurrentstate-of-the-art anodes are not capable of fully oxidizing ethanol toCO

Combinatorial approaches for efficient screening of multicomponent photocatalysts and fuel cell catalysts

Environmental issues and fossil fuel demands have propelled renewable energy research and development. Photocatalytic systems are inspired by artificial photosynthesis, which is capable of converting solar energy into chemical energy. Fuel cells, on the other hand, hold great potential for direct conversion of chemical energy into electricity. A rational combination of photocatalytic systems and fuel cells can effectively convert, store and utilize solar energy as compared with hybrid solar cell–battery systems. The critical issues for both the systems are to discover suitable and low-cost catalysts for chemical conversion with high efficiency. In general, catalysts involved with several synergistic components and an optimal recipe for each constituent should be derived. Traditional methods were based on pure empirical and trial-error testing, which are time consuming and labor intensive. Alternative method that can screen catalysts rapidly could be of great importance. In this mini review, preparation of sample arrays with various compositions and libraries suitable for combinatorial characterization is discussed. Next, the focus is on discussing several methods including scanning mass spectrometry, pH imaging and scanning electrochemical microscopy for efficient screening in serial. Successful implementation of these approaches has a potential to open up opportunities for identification and commercialization of efficient solar energy–harvesting catalysts.

Fuel Cells for Autonomous Underwater Vehicles

A long-distance performance is a significant parameter for mobile platforms. A key condition is a highly efficient source of energy. Fuel cells, i.e. electrochemical devices, capable of direct conversion of chemical energy accumulated in fuel into electrical energy, occurred to be relevant. In this paper there were presented the results of the analysis pertaining to the volumetric requirements of the system exploiting the fuel cell that is capable of ensuring the running time comparable with that of conventionally used rechargeable batteries.

生化学反応を利用した化学エネルギー駆動型圧力制御システム

A novel chemo-mechanical pressure control system for pumping applications was constructed and tested. The pressure control system utilizes direct conversion of chemical energy to mechanical energy by enzymatic reactions. In order to construct the system, glucose oxidase (GOD) and catalase (CAT) were immobilized onto a dialysis membrane with photosensitive resin. The enzyme immobilized membrane was functioned as a diaphragm of a reaction unit. Therefor, the reaction unit was divided into a top cell (gas phase) and a bottom cell (liquid phase). Characterization of the pressure control system was carried out by supplying hydrogen peroxide and glucose solution into the liquid cell, respectively. As a result, active pressure iincrease in the top cell induced by oxygen production due to decomposition of hydrogen peroxide and pressure decrease induced by oxygen consumption of GOD reaction. Thus, the pressure in the cell was successfully controlled by chemical energy. The possible application of the pressure controle system is a diaphragm pump which is driven with active pressure change.

Preliminary data on subsolidus phase equilibria in the La2O3-(Al2O3/Fe2O3)-Y2O3 and La2O3-(AI2O3/Fe2O3)-ZrO2 systems

A fuel cell is a device for direct conversion of chemical energy into electrical energy. Oxidant is fed to the cathode and reducent (fuel) to the anode. The electrolyte, through which the ion current flows, also prevents the mixing of oxidant and fuel. The principle of fuel cell operation was reported in 1839 by Sir William Grove [1]. For a description of fuel cell development see, for example, [2]. High temperature solid oxide fuel cells (SOFC) work at temperatures of up to 1000 °C. Due to the high operating temperatures of SOFC, the choice of materials is mainly limited to ceramics. A comprehensive review of materials for SOFC was published by Minh [3]. The solid electrolyte in SOFC cells is usually yttria stabilized cubic zirconia (YSZ). The oxygen accepts electrons at the cathode and moves as an ion through the dense Z r Q ceramic. At the anode ions combine with fuel and release electrons. The fuel is either hydrogen, a H2/CO mixture, or hydrocarbons because the high temperature of operation makes possible the internal (in situ) reforming of hydrocarbons with water vapour [4]. The advantage of SOFC is their high efficiency, of 50-60%, while some estimations are even up to a yield of 70-80% [5-8]. Also, nitrous oxides are not produced and the amount of CO2 released per kilowatt hour is, due to the high yield, around 50% less than for power sources based on combustion. Annually, around 109 US$ is invested in research and development of fuel cells, and this amount is growing, mainly due to environmental concerns [9-111. Due to the high operating temperatures and oxidizing atmosphere on the cathode side, only noble metals (platinum, for example) or oxides with low resistivity can be used for electrodes. Noble metals are unsuitable, partly because of problems with long-term stability, but mostly because of their high cost. At present semiconducting oxides (perovskites) based on doped LaMnO3 or LaCoO 3 are most often used as cathode materials. The cathode must be porous to permit the diffusion of oxygen to the zirconia electrolyte, and must have high electrical conductivity. The electrode polarization losses, related to irreversibilities in the electrochemical processes, are reduced if the electrode material possesses both ionic and electronic conductivity. If the material is an electronic conductor only, the electrochemical reactions can occur solely at the three-phase boundary of the

Materials Engineering and Fuel Cell Development

The direct conversion of chemical energy in a fuel cell has been one of the most challenging technological problems since a simple hydrogen/oxygen fuel cell was first demonstrated 150 years ago by Groves at the London Institution. Aqueous electrolyte fuel cells have been successfully used in space to power electrical equipment in the Apollo spacecraft and in the space shuttle, but terrestrial applications have been principally limited to a few specialized military and telecommunication applications.In the original concept of a fuel cell, a primary fuel (e.g., hydrogen, hydrocarbon) is reacted with oxygen in an electrochemical cell incorporating an acid electrolyte, namely:so as to convert the free energy of oxidation (ΔG°) of the fuel to carbon dioxide and water directly into electrical energy.Fuel cells are attractive in that theoretical thermodynamic energy/fuel conversion ratios given by the appropriate value of ΔG°/ΔH° (free energy change/enthalpy change) can be very high (e.g., ~95% for H2/O2 reaction at 298 K) compared to the limitations imposed on heat engines by the Carnot cycle efficiency, (T2−T1)/T2. However, in practice it has proved difficult to realize the high electrical/fuel conversion efficiencies promised by fuel cell systems. This is caused by problems associated with the electrochemical kinetics and/or the requirement that in the Faradaic reaction both mass and electron transfer must occur in a spatially restricted region where an electrode, an electrolyte, and one of the reacting phases (usually a gas) are in intimate contact. This region is often referred to as the three-phase boundary.

The direct conversion of chemical energy into electricity

Reviews the basic principles and thermodynamics of fuel cells and discusses practical examples and applications. Considerable progress has been made in applying basic knowledge to the development of practical fuel cell systems, at present the high capital cost and low long-term reliability, due mainly to problems of electrode kinetics and construction materials, are delaying the full commercial development of fuel cells.

Mechanochemistry of Cardiac Muscle

This investigation was designed to determine whether a defect in energy utilization exists in heart failure. Accordingly, the direct conversion of chemical energy to mechanical work was studied in right ventricular papillary muscles from normal cats and cats with experimental right ventricular failure secondary to pulmonary artery constriction. Energy production was inhibited by iodoacetic acid and N 2 . After resting or performing variable amounts of internal contractile element work under isometric conditions, muscles were instantly frozen, and the total amount of chemical energy (∼ P = creatine phosphate + ATP) used was correlated with work performed and the number of contractions. The contractile properties of papillary muscles from cats with heart failure were severely depressed. There was a significant depression in initial ∼P stores in muscles from cats with heart failure, but there was no significant change in the resting rate of ∼P utilization. Although the muscles from cats with heart failure performed, on the average, 13% as much work and were activated 64% as many times, the average amount of energy used was only 7% of that used by normal muscles. It is concluded that in this form of experimentally produced heart failure the utilization of ∼P is reduced but only in relation to the reduction in contractile element work and that the direct conversion of chemical energy to mechanical work is not an inefficient process in this state.

Mechanochemistry of cardia muscle. 3. Effects of norepinephrine on the utilization of high-energy phosphates.

Norepinephrine increases myocardial contractility and myocardial oxygen consumption (MV · O 2 ). It is not clear whether these phenomena are directly proportional or whether there is a disproportionate increase in MV · O 2 , signifying either uncoupling of oxidative phosphorylation or a direct increase in oxidative metabolism. Accordingly, the direct conversion of chemical energy to mechanical work was studied in control and norepinephrine-treated right ventricular papillary muscles from cats. Production of adenosine triphosphate (ATP) was inhibited by iodoacetic acid and N 2 . After resting or performing variable amounts of work, the muscles were instantly frozen, and the total amount of chemical energy (∼P = creatine phosphate + ATP) used was correlated with work performed and the number of contractions. There was no change in either the initial stores of energy or in the basal rate of energy utilization following treatment with norepinephrine. However, norepinephrine-treated muscles performing isometric work used 115% as much ∼P as control muscles in only 59% as many contractions and while performing only 87% as much work. Regression analysis of these data confirmed that norepinephrine-treated muscles used a greater amount of ∼P than do control muscles. Thus the increase in contractility induced by norepinephrine results in an increase in the amount of chemical energy released disproportionate to the amount of work performed, and the "oxygen wasting" effect of norepinephrine on heart muscle results from the increased utilization of energy associated with an increased contractile state.